Archive for February, 2017

Once in a while I share “fan mail” I get in response to my blog, and I thought the following example was unusually interesting.

I won’t bother to rebut the mix of misrepresentations, misinformation, etc. This is more for entertainment value.

WARNING: The language in the following is, shall we say, colorful. Don’t read any further if you are easily offended.

YOU’VE BEEN WARNED.

“Like every other idiot who thinks 7.4 billion human beings cannot alter our planet, you fail to ask yourself the most important question you should be asking: what if you’re wrong.

If you are wrong, and mankind is desequestering carbon, nitrogen, and hydrogen in the form of fossil fuels, then you are advocating the destruction of humanity through the reversal of natural climate engineering.

If you’re wrong and we continue to use fossil fuels, the species and all other mammals will be forever wiped out.

And you are so fucking arrogant, and so fucking lazy, as to not bother asking that simple question.

Why? Because it would be too much work for you to live without your fucking car.

Fuck you.

Go do your fucking homework asshole. Your “science” can’t explain the CO2 levels in the atmosphere, nor the melting Arctic ice cap, nor even why the ice ages occurred only in the northern hemisphere. You don’t understand a damn thing about weather or climate, or even basic atmospheric chemistry. All you know is your fucking ego.

How about this, asshole, tell me how much WATER has been brought up from fossil fuels, how much carbon, how much nitrogen, how much oxygen, and what percentage they increased their corresponding partial pressures in the atmosphere.

Then tell me what the climate was like when the atmospheric carbon was as high as it is now, and whether or not mammals existed.

By the way, asshole, The Oroville Dam is NOT a simple earthen dam, it is a SYSTEM, and that SYSTEM, including the concrete reinforced auxiliary spillway, has failed, because the system was designed to control the flow of water, and right now, there is no such control, and there are processes in place which are destroying the FOUNDATION of the auxiliary spillway and significantly reducing the capacity of the lake to hold water, and which is now presently flowing quite quickly down the mountain.

With the evacuation order lifted last evening, and ~185,000 residents returning to their homes in Oroville and surrounding communities, emergency repairs continue around the clock on the damaged emergency spillway at Oroville Dam. Yesterday morning (Feb. 14), a concrete pumper and boulders were being used to patch the main erosion features that developed when the emergency spillway was overtopped:

The water level of the lake is being reduced by 8 or 9 feet per day, and now stands at 880 ft., which is 21 feet below the top of the 901 ft.-elevation concrete weir that was overtopped a few days ago by 1.5 ft. The rapid lowering of the lake is being accomplished with a continuous 100,000 CFS flow over the main spillway (the same as the average flow over Niagara Falls) which was heavily damaged over a week ago:

Little more than one day of only about 10,000 CFS flow over the concrete weir of the emergency spillway caused unexpected erosion down into the highly fractured bedrock, which is what led to the evacuation orders as the continuing erosion back to the concrete weir led to fears that structure could be compromised:

I’ve been following a continuing discussion by outside experts here, and also following the forecasts of a series of new storms that will sweep through California over the next week.

Based upon everything I’ve seen, I’d say that for the foreseeable future, the dam facility is out of danger. Here’s why:

1) The 100,000 CFS flow through the (damaged) main spillway will, in all likelihood, keep the lake level below the 901 ft. elevation of the emergency spillway. Even though the next week of storms will cause as much as 7-14 inches of liquid-equivalent precipitation to fall, much of that will fall as snow except over a relatively small portion of the watershed. The 100,000 CFS flow rate through the main spillway could be increased to 150,000 CFS if needed.

2) As of yesterday, the main spillway damage was not eroding uphill, suggesting that portion is on bedrock. It is possible that the remaining concrete is actually more stable at higher flow rates, which creates a waterfall out and away from the bedrock the concrete flume is sitting on.

3) Spring snow melt usually occurs slowly enough that the main spillway will be able to keep up with it.

4) Even if the concrete weir is over-topped again, and erosion of the bedrock extends back to the concrete weir, that structure is very thick, and it is not at all obvious that it would fail. This is a big uncertainty, though, and if it ever gets to that point, evacuations would again be announced.

Note that all of this positive outcome depends upon the undamaged uphill portion of the main spillway remaining stable. This is why repairs to the hillside below the emergency spillway are being performed as fast as possible, in case the main spillway fails and the lake level rises uncontrollably, and then once again overtops the emergency spillway weir.

I believe that the use of the previously-untested emergency spillway, and the resulting damage, was actually a blessing in disguise. That structure was designed to handle 10-15 feet of water flowing over it, but it only took 1.6 ft of flow to cause substantial hillside erosion in less than 2 days. Now that the geology of that hillside has been revealed, engineers will be able to come up with an engineering solution so that if there ever is a catastrophic flooding event, the emergency spillway will be in a much better state to handle it without failure of the concrete weir, which could result in a ~30 ft. wall of water to cascade downstream.

After watching the Oroville Dam crisis evolve over the last several days, and reading various experts’ opinions about what might be going on both with both the facility itself and behind the scenes decision-making, I thought it might be time to step back and discuss where we are at, and where we might be going.

The Dam Spillway Situation

First of all, the immediate crisis has passed. At this writing (4 a.m. PST Tuesday), the lake level has been lowered to 11 feet below the emergency spillway, and is dropping at a rate of about 8 feet per day. The goal is to get it to about 50 feet below the top of the concrete weir of the emergency spillway, which was topped by 1.5 feet at the peak of the crisis.

That’s the good news.

The bad news is that in order to achieve this, the flow through the main concrete-lined spillway, which has been heavily damaged, has had to be increased to 100,000 cubic feet per second (CFS), creating a spectacular waterfall over the lip of the remaining portion of the concrete flume:

More on that later.

The other bad news is that the relatively brief use of the emergency spillway led to a lot more erosion into the rock below the concrete weir than engineers expected. This rapid erosion is why evacuations were suddenly ordered, since there were fears that it would backcut to the concrete weir, which was at risk of collapse:

One of two major eroded areas just below the emergency spillway of Oroville Dam (Feb. 13, 2017).

If that happened, a 30 ft. wall of water would cascade downstream. At least two large gouges are currently being patched with sacks of rock and some concrete. The emergency spillway was supposedly designed to handle 350,000 CFS, but it only took a day at 10,000 CFS to cause the damage, leading up to an official warning that the spillway could collapse within an hour and the mandatory evacuation order. (The main earthfill portion of the dam is in no danger, since the emergency spillway, 20 ft. below the level of the main dam, would keep the main dam from ever being topped).

My (admittedly non-expert) view of the situation is that the emergency spillway is of lesser concern at this point. Rains will return Wednesday night beginning a 7-day wet period during which 5 to 12 inches of water-equivalent precipitation will fall on the watershed:

Google Earth view of the watershed feeding Oroville Lake. Much of this area is above 4,500-5,000 ft. elevation, where winter precipitation usually falls as snow.

That might sound bad, but the good news is that most of that precipitation will fall as snow, except over the lake itself, in contrast to earlier warm rain events that led to the current crisis.

Despite the new precipitation, I suspect that they will be able to keep the lake level to around 850-860 feet or so, which is 40-50 feet below full-pool. It might briefly rise by 10-20 feet if the rain is exceptionally heavy. The main danger to Northern California dams is heavy rain events; spring snow melt typically occurs more slowly and is easier to handle by adjusting outflow from reservoirs.

I further suspect that concern will be shifted to the main spillway, the continuing heavy use of which is absolutely required in order to keep the lake level low enough to allow repairs to the emergency spillway, as long as there is significant runoff into the lake.

Close-up of damage to main spillway on Feb. 7; the concrete wall in the foreground has since been destroyed with considerable erosion of the adjacent hillside (SacBee photo).

The hydro plant generators have been shut down from debris, and they would have only allowed an additional 16,000 CFS outflow anyway. The diversion tunnels were damaged years ago and are unusable.

So, the damaged main spillway is essentially the only way that the reservoir can shed substantial volumes of water as rains occur, and as spring snow melt begins.

I predict that they will shut the main spillway down soon to see how fast the damage is eroding uphill. If I had to guess, I’d say that shutdown might actually happen today…a three hour shutdown will only reduce the lake level fall by 1 foot. They need to assess the situation, because…

A PR Disaster is Rapidly Approaching

From watching the daily press briefings, I think that the experts and emergency officials have been less than forthcoming on details. As dam expert Scott Cahill wrote yesterday, the public has been treated a little like children so far. Reporters’ questions have gone unanswered, and the experts opinions have careened between “no danger” and “imminent failure” in less than 24 hours. (Update: Scott Cahill has a new essay today about how no one is ever accountable anymore in disaster situations…it’s all review panels and committees….the buck is passed from person to person until no one knows who has the buck.)

This is NOT the way for “experts” to engender confidence in the public.

Of particular concern is the estimated 185,000 residents who have evacuated to higher ground, and are anxious to return to their homes. We live in an age where we want results now, and the longer these people have to wait with only general information being provided, the more anger and frustration will grow. Reporters are going to cover this frustration, with face-to-face interviews, and officials had better get ahead of the impending PR disaster while they can.

When will people be allowed home? I can only speculate. If emergency officials are being very cautious they might wait until the coming wet weather period has passed, which would be at least 10 days to make sure the lake does not rise too much, and until after they have verified the concrete flume of the main spillway isn’t eroding uphill very much.

Or, they could let people return at any time, warning them to keep alert for a possible future evacuation with little notice. I really dont know. If I had to guess, I’d say they will go the cautious route. But if they were to inspect the main spillway today and see only minor additional erosion uphill from where it previously was, maybe they will let people come home very soon.

No matter what happens in the coming days and weeks, Oroville Dam will remain an issue for months — maybe even years — to come. Repairs will be expensive and lengthy. And there will be second-guessing of decisions made, including the 12-year old report by experts that the emergency spillway was just fine as-is.

(A detailed chronological discussion of the Oroville issues by mainly geologists, along with some amazing photos, can be followed here.)

UPDATE: Mick West, Sacramento, provided this graphic which shows the volume of water that can be output from Lake Oroville at 100,000 CFS flow through the main spillway (area of the red box), versus what has flowed into the lake from precipitation in the last couple months (area under the blue curve). It suggests that the lake can probably be kept from completely filling again if 100,000 CFS outflow is maintained, with only temporary rises in lake level after heavy rain events:

I’ve had a little criticism here and on Facebook that I’m not a geologist, so I shouldn’t be second-guessing the Oroville Dam engineers. They called for evacuations last evening out of an abundance of caution. That the emergency spillway is no doubt built on bedrock, and so it is safe.

Well, if it was only out of an abundance of caution that evacuations were ordered, why did emergency officials claim that there might be only one hour until the concrete weir topping the emergency spillway would fail? Hmmm?

And take a look at one of the ravines that eroded from only a little over 24 hours of flow over the emergency spillway

One of two major eroded areas just below the emergency spillway of Oroville Dam (Feb. 13, 2017). The little yellow spots are people.

Does that erosion feature look like it’s cutting into bedrock? Even though the spillway is supposed to handle 250-350,000 CFS, it was only ~10,000 CFS total flow across the 1,700 ft. long weir that caused this.

The latest press conference held shortly after noon today suggested that officials are avoiding hard questions. At one point a reporter asked, “With two parts of the system compromised (the main spillway and emergency spillway), how secure can people be?“. The speaker was not allowed to answer the question.

I honestly don’t know what’s going on, but if I lived in the flood plain (and now one of the near-200,000 people evacuated), I’d be wanting some more definitive information.

With daylight and Oroville Lake water levels now 4 feet below the lip of the emergency spillway, we can see that the area of concern is a gouge which developed near the far end of the concrete weir, and was eroding uphill toward that structure; for scale, those yellow spots are people inspecting the gouge (click images for full-size):

A wide-angle view (KCRA-TV helicopter frame grabs) shows the main, heavily damaged spillway which still has a huge 100,000 CFS flow continuing in an attempt to reduce the lake level as much as possible:

Rocks have been bagged overnight and helicopters will soon start filling the gouge:

The 100,000 CFS flow through the main spillway continues to erode the break in the concrete flume, but engineers are not worried about the damage eroding uphill and damaging the main portion of the dam:

So, it turns out all of that bedrock that made the Oroville Dam design so fail-safe is not going to stand in the way of Mother Nature.

Mandatory evacuations have been ordered, and the emergency spillway is expected to fail within the hour.

Flash flood warnings have been issued. This will affect Oroville all the way to Sacramento I assume.

UPDATE: Evening briefing announcement that a hole has developed slightly downhill of the base of the 1,700 ft-long concrete portion of the emergency spillway. Here’s a screenshot from this evening from the KCRA-TV helicopter with my annotation of my *guess* of where the problem might be (they were NOT specific in the press conference). They said if the hole migrates uphill much farther and undercuts the spillway, the concrete portion could fail, which is why the evacuations were announced. (Another view I’m hearing is the problem is at the left end of the spillway, not at the right end.)

The flow out the main spillway has been increased to 100,000 CFS, which should stop the flow over the emergency spillway tonight. But even if the concrete does not fail tonight, I suspect the problem won’t go away as new rain systems are forecast in the coming week, and snow melt season hasn’t even started yet.

UPDATE:

DWR plans to use helicopters to drop rocks to fill in the gouge in the Oroville Auxilliary Spillway to stabilize.

While it is said, “never say never”, after researching this issue I’m pretty convinced that it would be nearly impossible for the Oroville Dam to fail.

Even though it is an earthfill embankment dam, which can be destroyed if the dam is topped, the following Metabunk graphic demonstrates why the Oroville design is virtually foolproof:

The emergency spillway (which is now in use) drains excess water along its 1,700 ft length when the lake level exceeds 901 ft. At this writing the lake level is 902.5 ft, which is 1.5 ft. above the lip of the spillway.

The water level would have to rise another 18.5 feet (!) in order to reach the top of the dam itself, which would never happen because the emergency spillway flow (which occurs over a natural ridge made of bedrock) would handle the excess flow long before the lake level ever reached that point.

Now, is there any scenario in which this might happen? I’m not a hydrologist, so I can’t answer that. But if there was a sudden warm spell in the next few weeks with say, 10-20 inches of rain over the watershed melting most of the mountain snowpack, adding tremendously to the inflow into the lake, I’m sure we would see a much greater flow over the emergency spillway. But I suspect it would never reach the top of the dam itself. Nevertheless, there would be a massive flooding event downstream in the Feather and Sacramento Rivers.

The last couple of days have not made me very confident in the predictions of engineers associated with the Oroville Dam.

While I am a climate researcher, and not hydrologist, it took me less than an hour midday yesterday (see comments here) to estimate that the emergency spillway would be breached around 9 a.m. PST this morning. I was off by an hour…it was breached at 8 a.m.

Furthermore we haven’t even entered snow melt season yet, and already Lake Oroville has exceeded its 100% capacity (here’s yesterday’s plot, at 97%):

Lake Oroville water levels in different years, showing the current level is unprecedented for so this date, and rapidly approaching a 100% full state.

So, I am merely raising the question: if engineers were reluctant to predict the current topping of the emergency spillway — a relatively benign event that was rather easily predicted — how much confidence can we have that the damage to the main spillway won’t compromise the dam?

I think engineers are going to have to be a little more forthcoming about whether such a failure — which threatens thousands of people immediately downstream — is indeed possible in the coming weeks and months as the massive mountain snowpack melts and continues to fill the lake — and continues to erode the spillways.

UPDATE:As of 9 a.m. PST, the water level has increased to 901.24 ft., and water is overflowing the 1,700 ft. long emergency spillway.

For the first time in the 50 year history of Oroville Dam, Lake Oroville has exceeded its design limit as of 3 a.m. PST this morning, reaching 900.1 ft. elevation.

The inflow rate into the reservoir continues to exceed the outflow rate, increasing the probability of the first-ever use of the emergency spillway. This would cause massive erosion of the hillside, which in this Google Earth image is to the left of the narrow concrete spillway (2015 imagery, reservoir 50% full):

I have made an estimate of when the emergency spillway might be breached based upon rates of inflow and outflow; the following chart suggests around 8 a.m. this morning:

These (unofficial) model-projected levels in the above chart assume measured inflow into the reservoir continues its steady decrease, and the outflow remains the same as it has been since 8 p.m. last night, when engineers reduced the flow through the damaged concrete spillway to avoid damage to power line towers:

Even if flow through the concrete spillway is increased to full-flow, the topping of the emergency spillway would only be delayed by an hour or so (9 a.m.). Lake levels would not keep increasing afterward, as suggested in the above chart… the model estimates are just meant to suggest we are likely headed to a breach of the emergency spillway, which will then provide an additional outflow channel for the lake.

I have no idea whether engineers have any “tricks up their sleeve” to avoid the emergency water release. The electricity generating turbines have been shut down due to debris in the water. I suspect we will be seeing some rather dramatic (and very muddy) video later today.

With a winter of phenomenal heavy rains and snow (over 400 inches so far at some Sierra Nevada locations), Lake Oroville 65 miles north of Sacramento is literally entering uncharted territory in its 50 year history.

As the following chart shows, the reservoir is rapidly approaching its design capacity:

Lake Oroville water levels in different years, showing the current level is unprecedented for so early in the year, and rapidly approaching a 100% full state.

While the reservoir has been nearly full in some previous years, note that this occurred in early summer, after mountain snowmelt. We have not even reached snowmelt season yet, suggesting a continuing flooding problem in the coming months.

A few days ago engineers reassured us there was still 20% of the reservoir unfilled. Then yesterday morning it was 90% full. This morning at 5 a.m. it was 97% full, and at the rate it is filling, tonight or tomorrow it will likely overflow the emergency spillway for the first time ever. Here’s a Google Earth image of the dam in April 2015 (when the reservoir was only 50% full); the wooded area to the left of the narrow concrete spillway is where the water will likely overflow this weekend:

To make matters worse, the concrete spillway has been badly damaged due to partial failure, which will likely get only worse as it is used to avoid the emergency spillway for as long as possible:

If water overflows down the emergency spillway, there will be a mess created in the Feather River due to soil, rock, and tree debris, threatening young salmon. The Feather River then flows into the Sacramento River farther downstream. Emergency officials are beginning to discuss evacuation preparations downstream.